Summary
Q: How can I specify an external harddrive as the download target for the Mist blockchain?
A: The answer for the Mac version is in Method 1 in In Mist browser how can I move the data (blockchain) to another drive on Mac OSX?. The Linux version is below.
Q: Even if the blockchain data gets corrupted somehow, it won't affect my wallets, right? I can keep them in a folder on my computer instead of the external harddrive, yes or no?
A: Yes. Just make sure that you backup ~/.ethereum/keystore.
Q: I. e. I would prefer having the blockchain data on an external drive and the wallet files on my laptop harddrive. Possible or not?
A: Yes.
The Details
The default subdirectory where your Ethereum data files are stored on Linux is ~/.ethereum .
Within this subdirectory, your blockchain data is stored in the subdirectory chaindata, i.e., ~/.ethereum/chaindata .
Let's assume that your new drive is mounted on /mnt/extdrive1 for this example.
Copy your ~/.ethereum/chaindata subdirectory into your new location /mnt/extdrive1/Ethereum/chaindata using the following command:
mkdir /mnt/extdrive1/Ethereum
cp -rpv ~/.ethereum/chaindata /mnt/extdrive1/Ethereum/
A copy of your Ethereum chaindata subdirectory will now be located in /mnt/extdrive1/Ethereum/chaindata.
Rename your default Ethereum chaindata subdirectory for testing:
mv ~/.ethereum/chaindata ~/.ethereum/OldChaindata_to_delete_when_tested
Soft link your new chaindata subdirectory back to the default location:
ln -s /mnt/extdrive1/Ethereum/chaindata ~/.ethereum/chaindata
Test out your Mist browser and delete your old chaindata directory ONLY AFTER your testing is successful:
rm -rf ~/.ethereum/OldChaindata_to_delete_when_tested
References
